# NAME
Dancer::Plugin::Passphrase - Passphrases and Passwords as objects for Dancer
# SYNOPSIS
This plugin manages the hashing of passwords for Dancer apps, allowing
developers to follow cryptography best practices without having to
become a cryptography expert.
It uses the bcrypt algorithm as the default, while also supporting any
hashing function provided by [Digest](https://metacpan.org/pod/Digest)
# USAGE
package MyWebService;
use Dancer ':syntax';
use Dancer::Plugin::Passphrase;
post '/login' => sub {
my $phrase = passphrase( param('my password') )->generate;
# $phrase is now an object that contains RFC 2307 representation
# of the hashed passphrase, along with the salt, and other metadata
# You should store $phrase->rfc2307() for use later
};
get '/protected' => sub {
# Retrieve $stored_rfc_2307_string, like we created above.
# IT MUST be a valid RFC 2307 string
if ( passphrase( param('my password') )->matches( $stored_rfc_2307 ) ) {
# Passphrase matches!
}
};
get '/generate_new_password' => sub {
return passphrase->generate_random;
};
# KEYWORDS
## passphrase
Given a plaintext password, it returns a Dancer::Plugin::Passphrase
object that you can generate a new hash from, or match against a stored hash.
# MAIN METHODS
## generate
Generates an RFC 2307 representation of the hashed passphrase
that is suitable for storage in a database.
my $pass = passphrase('my passphrase')->generate;
You should store `$phrase-`rfc\_2307()> in your database. For convenience
the object will automagically return the RFC 2307 representation when no
method is called on it.
Accepts a hashref of options to specify what kind of hash should be
generated. All options settable in the config file are valid.
If you specify only the algorithm, the default settings for that algorithm will be used.
A cryptographically random salt is used if salt is not defined.
Only if you specify the empty string will an empty salt be used
This is not recommended, and should only be used to upgrade old insecure hashes
my $phrase = passphrase('my password')->generate({
algorithm => '', # What algorithm is used to generate the hash
cost => '', # Cost / Work Factor if using bcrypt
salt => '', # Manually specify salt if using a salted digest
});
## matches
Matches a plaintext password against a stored hash.
Returns 1 if the hash of the password matches the stored hash.
Returns undef if they don't match or if there was an error
Fail-Secure, rather than Fail-Safe.
passphrase('my password')->matches($stored_rfc_2307_string);
$stored\_rfc\_2307\_string __MUST__ be a valid RFC 2307 string,
as created by [generate()](#passphrase__generate)
An RFC 2307 string is made up of a scheme identifier, followed by a
base64 encoded string. The base64 encoded string should contain
the password hash and the salt concatenated together - in that order.
'{'.$scheme.'}'.encode_base64($hash . $salt, '');
Where `$scheme` can be any of the following and their unsalted variants,
which have the leading S removed. CRYPT will be Bcrypt.
SMD5 SSHA SSHA224 SSHA256 SSHA384 SSHA512 CRYPT
A complete RFC2307 string looks like this:
{SSHA}K3LAbIjRL5CpLzOlm3/HzS3qt/hUaGVTYWx0
This is the format created by [generate()](#passphrase__generate)
## generate\_random
Generates and returns any number of cryptographically random
characters from the url-safe base64 charater set.
my $rand_pass = passphrase->generate_random;
The passwords generated are suitable for use as
temporary passwords or one-time authentication tokens.
You can configure the length and the character set
used by passing a hashref of options.
my $rand_pass = passphrase->generate_random({
length => 32,
charset => ['a'..'z', 'A'..'Z'],
});
# ADDITIONAL METHODS
The methods are only applicable once you have called `generate`
passphrase( 'my password' )->generate->rfc2307; # CORRECT
passphrase( 'my password' )->rfc2307; # INCORRECT, Returns undef
## rfc2307
Returns the rfc2307 representation from a `Dancer::Plugin::Passphrase` object.
passphrase('my password')->generate->rfc2307;
## scheme
Returns the scheme name from a `Dancer::Plugin::Passphrase` object.
This is the scheme name as used in the RFC 2307 representation
passphrase('my password')->generate->scheme;
The scheme name can be any of the following, and will always be capitalized
SMD5 SSHA SSHA224 SSHA256 SSHA384 SSHA512 CRYPT
MD5 SHA SHA224 SHA256 SHA384 SHA512
## algorithm
Returns the algorithm name from a `Dancer::Plugin::Passphrase` object.
The algorithm name can be anything that is accepted by `Digest-`new($alg)>
This includes any modules in the `Digest::` Namespace
passphrase('my password')->generate->algorithm;
## cost
Returns the bcrypt cost from a `Dancer::Plugin::Passphrase` object.
Only works when using the bcrypt algorithm, returns undef for other algorithms
passphrase('my password')->generate->cost;
## salt\_raw
Returns the raw salt from a `Dancer::Plugin::Passphrase` object.
passphrase('my password')->generate->salt_raw;
Can be defined, but false - The empty string is technically a valid salt.
Returns `undef` if there is no salt.
## hash\_raw
Returns the raw hash from a `Dancer::Plugin::Passphrase` object.
passphrase('my password')->generate->hash_raw;
## salt\_hex
Returns the hex-encoded salt from a `Dancer::Plugin::Passphrase` object.
Can be defined, but false - The empty string is technically a valid salt.
Returns `undef` if there is no salt.
passphrase('my password')->generate->salt_hex;
## hash\_hex
Returns the hex-encoded hash from a `Dancer::Plugin::Passphrase` object.
passphrase('my password')->generate->hash_hex;
## salt\_base64
Returns the base64 encoded salt from a `Dancer::Plugin::Passphrase` object.
Can be defined, but false - The empty string is technically a valid salt.
Returns `undef` if there is no salt.
passphrase('my password')->generate->salt_base64;
## hash\_base64
Returns the base64 encoded hash from a `Dancer::Plugin::Passphrase` object.
passphrase('my password')->generate->hash_base64;
## plaintext
Returns the plaintext password as originally supplied to the [passphrase](https://metacpan.org/pod/passphrase) keyword.
passphrase('my password')->generate->plaintext;
# MORE INFORMATION
## Purpose
The aim of this module is to help you store new passwords in a secure manner,
whilst still being able to verify and upgrade older passwords.
Cryptography is a vast and complex field. Many people try to roll their own
methods for securing user data, but succeed only in coming up with
a system that has little real security.
This plugin provides a simple way of managing that complexity, allowing
developers to follow crypto best practice without having to become an expert.
## Rationale
The module defaults to hashing passwords using the bcrypt algorithm, returning them
in RFC 2307 format.
RFC 2307 describes an encoding system for passphrase hashes, as used in the "userPassword"
attribute in LDAP databases. It encodes hashes as ASCII text, and supports several
passphrase schemes by starting the encoding with an alphanumeric scheme identifier enclosed
in braces.
RFC 2307 only specifies the `MD5`, and `SHA` schemes - however in real-world usage,
schemes that are salted are widely supported, and are thus provided by this module.
Bcrypt is an adaptive hashing algorithm that is designed to resist brute
force attacks by including a cost (aka work factor). This cost increases
the computational effort it takes to compute the hash.
SHA and MD5 are designed to be fast, and modern machines compute a billion
hashes a second. With computers getting faster every day, brute forcing
SHA hashes is a very real problem that cannot be easily solved.
Increasing the cost of generating a bcrypt hash is a trivial way to make
brute forcing ineffective. With a low cost setting, bcrypt is just as secure
as a more traditional SHA+salt scheme, and just as fast. Increasing the cost
as computers become more powerful keeps you one step ahead
For a more detailed description of why bcrypt is preferred, see this article:
[http://codahale.com/how-to-safely-store-a-password/](http://codahale.com/how-to-safely-store-a-password/)
## Configuration
In your applications config file, you can set the default hashing algorithm,
and the default settings for every supported algorithm. Calls to
[generate()](#passphrase__generate) will use the default settings
for that algorithm specified in here.
You can override these defaults when you call [generate()](#passphrase__generate).
If you do no configuration at all, the default is to bcrypt with a cost of 4, and
a strong psuedo-random salt.
plugins:
Passphrase:
default: Bcrypt
Bcrypt:
cost: 8
## Storage in a database
You should be storing the RFC 2307 string in your database, it's the easiest way
to use this module. You could store the `raw_salt`, `raw_hash`, and `scheme`
separately, but this strongly discouraged. RFC 2307 strings are specifically
designed for storing hashed passwords, and should be used wherever possible.
The length of the string produced by [generate()](#passphrase__generate) can
vary dependent on your settings. Below is a table of the lengths generated
using default settings.
You will need to make sure your database columns are at least this long.
If the string gets truncated, the password can _never_ be validated.
ALGORITHM LENGTH EXAMPLE RFC 2307 STRING
Bcrypt 68 {CRYPT}$2a$04$MjkMhQxasFQod1qq56DXCOvWu6YTWk9X.EZGnmSSIbbtyEBIAixbS
SHA-512 118 {SSHA512}lZG4dZ5EU6dPEbJ1kBPPzEcupFloFSIJjiXCwMVxJXOy/x5qhBA5XH8FiUWj7u59onQxa97xYdqje/fwY5TDUcW1Urplf3KHMo9NO8KO47o=
SHA-384 98 {SSHA384}SqZF5YYyk4NdjIM8YgQVfRieXDxNG0dKH4XBcM40Eblm+ribCzdyf0JV7i2xJvVHZsFSQNcuZPKtiTMzDyOU+w==
SHA-256 74 {SSHA256}xsJHNzPlNCpOZ41OkTfQOU35ZY+nRyZFaM8lHg5U2pc0xT3DKNlGW2UTY0NPYsxU
SHA-224 70 {SSHA224}FTHNkvKOdyX1d6f45iKLVxpaXZiHel8pfilUT1dIZ5u+WIUyhDGxLnx72X0=
SHA-1 55 {SSHA}Qsaao/Xi/bYTRMQnpHuD3y5nj02wbdcw5Cek2y2nLs3pIlPh
MD5 51 {SMD5}bgfLiUQWgzUm36+nBhFx62bi0xdwTp+UpEeNKDxSLfM=
## Common Mistakes
Common mistakes people make when creating their own solution. If any of these
seem familiar, you should probably be using this module
- Passwords are stored as plain text for a reason
There is never a valid reason to store a password as plain text.
Passwords should be reset and not emailed to customers when they forget.
Support people should be able to login as a user without knowing the users password.
No-one except the user should know the password - that is the point of authentication.
- No-one will ever guess our super secret algorithm!
Unless you're a cryptography expert with many years spent studying
super-complex maths, your algorithm is almost certainly not as secure
as you think. Just because it's hard for you to break doesn't mean
it's difficult for a computer.
- Our application-wide salt is "Sup3r\_S3cret\_L0ng\_Word" - No-one will ever guess that.
This is common misunderstanding of what a salt is meant to do. The purpose of a
salt is to make sure the same password doesn't always generate the same hash.
A fresh salt needs to be created each time you hash a password. It isn't meant
to be a secret key.
- We generate our random salt using `rand`.
`rand` isn't actually random, it's a non-unform pseudo-random number generator,
and not suitable for cryptographic applications. Whilst this module also defaults to
a PRNG, it is better than the one provided by `rand`. Using a true RNG is a config
option away, but is not the default as it it could potentially block output if the
system does not have enough entropy to generate a truly random number
- We use `md5(pass.salt)`, and the salt is from `/dev/random`
MD5 has been broken for many years. Commodity hardware can find a
hash collision in seconds, meaning an attacker can easily generate
the correct MD5 hash without using the correct password.
- We use `sha(pass.salt)`, and the salt is from `/dev/random`
SHA isn't quite as broken as MD5, but it shares the same theoretical
weaknesses. Even without hash collisions, it is vulnerable to brute forcing.
Modern hardware is so powerful it can try around a billion hashes a second.
That means every 7 chracter password in the range \[A-Za-z0-9\] can be cracked
in one hour on your average desktop computer.
- If the only way to break the hash is to brute-force it, it's secure enough
It is unlikely that your database will be hacked and your hashes brute forced.
However, in the event that it does happen, or SHA512 is broken, using this module
gives you an easy way to change to a different algorithm, while still allowing
you to validate old passphrases
# KNOWN ISSUES
If you see errors like this
Wide character in subroutine entry
or
Input must contain only octets
The `MD5`, `bcrypt`, and `SHA` algorithms can't handle chracters with an ordinal
value above 255, producing errors like this if they encounter them.
It is not possible for this plugin to automagically work out the correct
encoding for a given string.
If you see errors like this, then you probably need to use the [Encode](https://metacpan.org/pod/Encode) module
to encode your text as UTF-8 (or whatever encoding it is) before giving it
to `passphrase`.
Text encoding is a bag of hurt, and errors like this are probably indicitive
of deeper problems within your app's code.
You will save yourself a lot of trouble if you read up on the
[Encode](https://metacpan.org/pod/Encode) module sooner rather than later.
For further reading on UTF-8, unicode, and text encoding in perl,
see [http://training.perl.com/OSCON2011/index.html](http://training.perl.com/OSCON2011/index.html)
# SEE ALSO
[Dancer](https://metacpan.org/pod/Dancer), [Digest](https://metacpan.org/pod/Digest), [Crypt::Eksblowfish::Bcrypt](https://metacpan.org/pod/Crypt::Eksblowfish::Bcrypt), [Dancer::Plugin::Bcrypt](https://metacpan.org/pod/Dancer::Plugin::Bcrypt)
# AUTHOR
James Aitken
# COPYRIGHT AND LICENSE
This software is copyright (c) 2012 by James Aitken.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.